// This file is part of Eigen, a lightweight C++ template library
// for linear algebra.
//
// Copyright (C) 2007-2009 Benoit Jacob <jacob.benoit.1@gmail.com>
// Copyright (C) 2009-2010 Gael Guennebaud <gael.guennebaud@inria.fr>
//
// This Source Code Form is subject to the terms of the Mozilla
// Public License v. 2.0. If a copy of the MPL was not distributed
// with this file, You can obtain one at http://mozilla.org/MPL/2.0/.

#ifndef EIGEN_DIAGONAL_H
#define EIGEN_DIAGONAL_H

namespace Eigen {

/** \class Diagonal
  * \ingroup Core_Module
  *
  * \brief Expression of a diagonal/subdiagonal/superdiagonal in a matrix
  *
  * \param MatrixType the type of the object in which we are taking a sub/main/super diagonal
  * \param DiagIndex the index of the sub/super diagonal. The default is 0 and it means the main diagonal.
  *              A positive value means a superdiagonal, a negative value means a subdiagonal.
  *              You can also use DynamicIndex so the index can be set at runtime.
  *
  * The matrix is not required to be square.
  *
  * This class represents an expression of the main diagonal, or any sub/super diagonal
  * of a square matrix. It is the return type of MatrixBase::diagonal() and MatrixBase::diagonal(Index) and most of the
  * time this is the only way it is used.
  *
  * \sa MatrixBase::diagonal(), MatrixBase::diagonal(Index)
  */

namespace internal {
    template <typename MatrixType, int DiagIndex> struct traits<Diagonal<MatrixType, DiagIndex>> : traits<MatrixType>
    {
        typedef typename ref_selector<MatrixType>::type MatrixTypeNested;
        typedef typename remove_reference<MatrixTypeNested>::type _MatrixTypeNested;
        typedef typename MatrixType::StorageKind StorageKind;
        enum
        {
            RowsAtCompileTime = (int(DiagIndex) == DynamicIndex || int(MatrixType::SizeAtCompileTime) == Dynamic) ?
                                    Dynamic :
                                    (EIGEN_PLAIN_ENUM_MIN(MatrixType::RowsAtCompileTime - EIGEN_PLAIN_ENUM_MAX(-DiagIndex, 0),
                                                          MatrixType::ColsAtCompileTime - EIGEN_PLAIN_ENUM_MAX(DiagIndex, 0))),
            ColsAtCompileTime = 1,
            MaxRowsAtCompileTime = int(MatrixType::MaxSizeAtCompileTime) == Dynamic ?
                                       Dynamic :
                                       DiagIndex == DynamicIndex ?
                                       EIGEN_SIZE_MIN_PREFER_FIXED(MatrixType::MaxRowsAtCompileTime, MatrixType::MaxColsAtCompileTime) :
                                       (EIGEN_PLAIN_ENUM_MIN(MatrixType::MaxRowsAtCompileTime - EIGEN_PLAIN_ENUM_MAX(-DiagIndex, 0),
                                                             MatrixType::MaxColsAtCompileTime - EIGEN_PLAIN_ENUM_MAX(DiagIndex, 0))),
            MaxColsAtCompileTime = 1,
            MaskLvalueBit = is_lvalue<MatrixType>::value ? LvalueBit : 0,
            Flags = (unsigned int)_MatrixTypeNested::Flags & (RowMajorBit | MaskLvalueBit | DirectAccessBit) &
                    ~RowMajorBit,  // FIXME DirectAccessBit should not be handled by expressions
            MatrixTypeOuterStride = outer_stride_at_compile_time<MatrixType>::ret,
            InnerStrideAtCompileTime = MatrixTypeOuterStride == Dynamic ? Dynamic : MatrixTypeOuterStride + 1,
            OuterStrideAtCompileTime = 0
        };
    };
}  // namespace internal

template <typename MatrixType, int _DiagIndex> class Diagonal : public internal::dense_xpr_base<Diagonal<MatrixType, _DiagIndex>>::type
{
public:
    enum
    {
        DiagIndex = _DiagIndex
    };
    typedef typename internal::dense_xpr_base<Diagonal>::type Base;
    EIGEN_DENSE_PUBLIC_INTERFACE(Diagonal)

    EIGEN_DEVICE_FUNC
    explicit inline Diagonal(MatrixType& matrix, Index a_index = DiagIndex) : m_matrix(matrix), m_index(a_index)
    {
        eigen_assert(a_index <= m_matrix.cols() && -a_index <= m_matrix.rows());
    }

    EIGEN_INHERIT_ASSIGNMENT_OPERATORS(Diagonal)

    EIGEN_DEVICE_FUNC
    inline Index rows() const
    {
        return m_index.value() < 0 ? numext::mini<Index>(m_matrix.cols(), m_matrix.rows() + m_index.value()) :
                                     numext::mini<Index>(m_matrix.rows(), m_matrix.cols() - m_index.value());
    }

    EIGEN_DEVICE_FUNC EIGEN_CONSTEXPR inline Index cols() const EIGEN_NOEXCEPT { return 1; }

    EIGEN_DEVICE_FUNC EIGEN_CONSTEXPR inline Index innerStride() const EIGEN_NOEXCEPT { return m_matrix.outerStride() + 1; }

    EIGEN_DEVICE_FUNC EIGEN_CONSTEXPR inline Index outerStride() const EIGEN_NOEXCEPT { return 0; }

    typedef typename internal::conditional<internal::is_lvalue<MatrixType>::value, Scalar, const Scalar>::type ScalarWithConstIfNotLvalue;

    EIGEN_DEVICE_FUNC
    inline ScalarWithConstIfNotLvalue* data() { return &(m_matrix.coeffRef(rowOffset(), colOffset())); }
    EIGEN_DEVICE_FUNC
    inline const Scalar* data() const { return &(m_matrix.coeffRef(rowOffset(), colOffset())); }

    EIGEN_DEVICE_FUNC
    inline Scalar& coeffRef(Index row, Index)
    {
        EIGEN_STATIC_ASSERT_LVALUE(MatrixType)
        return m_matrix.coeffRef(row + rowOffset(), row + colOffset());
    }

    EIGEN_DEVICE_FUNC
    inline const Scalar& coeffRef(Index row, Index) const { return m_matrix.coeffRef(row + rowOffset(), row + colOffset()); }

    EIGEN_DEVICE_FUNC
    inline CoeffReturnType coeff(Index row, Index) const { return m_matrix.coeff(row + rowOffset(), row + colOffset()); }

    EIGEN_DEVICE_FUNC
    inline Scalar& coeffRef(Index idx)
    {
        EIGEN_STATIC_ASSERT_LVALUE(MatrixType)
        return m_matrix.coeffRef(idx + rowOffset(), idx + colOffset());
    }

    EIGEN_DEVICE_FUNC
    inline const Scalar& coeffRef(Index idx) const { return m_matrix.coeffRef(idx + rowOffset(), idx + colOffset()); }

    EIGEN_DEVICE_FUNC
    inline CoeffReturnType coeff(Index idx) const { return m_matrix.coeff(idx + rowOffset(), idx + colOffset()); }

    EIGEN_DEVICE_FUNC
    inline const typename internal::remove_all<typename MatrixType::Nested>::type& nestedExpression() const { return m_matrix; }

    EIGEN_DEVICE_FUNC
    inline Index index() const { return m_index.value(); }

protected:
    typename internal::ref_selector<MatrixType>::non_const_type m_matrix;
    const internal::variable_if_dynamicindex<Index, DiagIndex> m_index;

private:
    // some compilers may fail to optimize std::max etc in case of compile-time constants...
    EIGEN_DEVICE_FUNC EIGEN_STRONG_INLINE EIGEN_CONSTEXPR Index absDiagIndex() const EIGEN_NOEXCEPT
    {
        return m_index.value() > 0 ? m_index.value() : -m_index.value();
    }
    EIGEN_DEVICE_FUNC EIGEN_STRONG_INLINE EIGEN_CONSTEXPR Index rowOffset() const EIGEN_NOEXCEPT { return m_index.value() > 0 ? 0 : -m_index.value(); }
    EIGEN_DEVICE_FUNC EIGEN_STRONG_INLINE EIGEN_CONSTEXPR Index colOffset() const EIGEN_NOEXCEPT { return m_index.value() > 0 ? m_index.value() : 0; }
    // trigger a compile-time error if someone try to call packet
    template <int LoadMode> typename MatrixType::PacketReturnType packet(Index) const;
    template <int LoadMode> typename MatrixType::PacketReturnType packet(Index, Index) const;
};

/** \returns an expression of the main diagonal of the matrix \c *this
  *
  * \c *this is not required to be square.
  *
  * Example: \include MatrixBase_diagonal.cpp
  * Output: \verbinclude MatrixBase_diagonal.out
  *
  * \sa class Diagonal */
template <typename Derived> EIGEN_DEVICE_FUNC inline typename MatrixBase<Derived>::DiagonalReturnType MatrixBase<Derived>::diagonal()
{
    return DiagonalReturnType(derived());
}

/** This is the const version of diagonal(). */
template <typename Derived> EIGEN_DEVICE_FUNC inline typename MatrixBase<Derived>::ConstDiagonalReturnType MatrixBase<Derived>::diagonal() const
{
    return ConstDiagonalReturnType(derived());
}

/** \returns an expression of the \a DiagIndex-th sub or super diagonal of the matrix \c *this
  *
  * \c *this is not required to be square.
  *
  * The template parameter \a DiagIndex represent a super diagonal if \a DiagIndex > 0
  * and a sub diagonal otherwise. \a DiagIndex == 0 is equivalent to the main diagonal.
  *
  * Example: \include MatrixBase_diagonal_int.cpp
  * Output: \verbinclude MatrixBase_diagonal_int.out
  *
  * \sa MatrixBase::diagonal(), class Diagonal */
template <typename Derived> EIGEN_DEVICE_FUNC inline typename MatrixBase<Derived>::DiagonalDynamicIndexReturnType MatrixBase<Derived>::diagonal(Index index)
{
    return DiagonalDynamicIndexReturnType(derived(), index);
}

/** This is the const version of diagonal(Index). */
template <typename Derived>
EIGEN_DEVICE_FUNC inline typename MatrixBase<Derived>::ConstDiagonalDynamicIndexReturnType MatrixBase<Derived>::diagonal(Index index) const
{
    return ConstDiagonalDynamicIndexReturnType(derived(), index);
}

/** \returns an expression of the \a DiagIndex-th sub or super diagonal of the matrix \c *this
  *
  * \c *this is not required to be square.
  *
  * The template parameter \a DiagIndex represent a super diagonal if \a DiagIndex > 0
  * and a sub diagonal otherwise. \a DiagIndex == 0 is equivalent to the main diagonal.
  *
  * Example: \include MatrixBase_diagonal_template_int.cpp
  * Output: \verbinclude MatrixBase_diagonal_template_int.out
  *
  * \sa MatrixBase::diagonal(), class Diagonal */
template <typename Derived>
template <int Index_>
EIGEN_DEVICE_FUNC inline typename MatrixBase<Derived>::template DiagonalIndexReturnType<Index_>::Type MatrixBase<Derived>::diagonal()
{
    return typename DiagonalIndexReturnType<Index_>::Type(derived());
}

/** This is the const version of diagonal<int>(). */
template <typename Derived>
template <int Index_>
EIGEN_DEVICE_FUNC inline typename MatrixBase<Derived>::template ConstDiagonalIndexReturnType<Index_>::Type MatrixBase<Derived>::diagonal() const
{
    return typename ConstDiagonalIndexReturnType<Index_>::Type(derived());
}

}  // end namespace Eigen

#endif  // EIGEN_DIAGONAL_H
